Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!unmvax!pprg.unm.edu!hc!lll-winken!netsys!vector!telecom-gateway From: westmark!dave@rutgers.edu (Dave Levenson) Newsgroups: comp.dcom.telecom Subject: Re: Subscriber's Line Cross-connected Message-ID: Date: 12 Feb 89 05:02:31 GMT Sender: news@vector.UUCP Organization: Westmark, Inc., Warren, NJ, USA Lines: 21 Approved: telecom-request@vector.uucp X-Submissions-To: telecom@eecs.nwu.edu X-Administrivia-To: telecom-request@vector.uucp X-TELECOM-Digest: volume 9, issue 59, message 2 of 6 In article , amdcad!amdcad.AMD.COM!rpw3@ames.arc.nasa.gov (Rob Warnock) writes: ... > There exist boxes (try Radio Shack) that show you if a phone line is > "off hook". (Basically, they measure the voltage.) And if your modem > is at all standard, it will assert "Data Set Ready" iff it is off-hook. ... If your modem is Hayes-compatible, it asserts DSR whenever it is powered up, whether or not it is off-hook. But if you flip one of its configuration switches, you can enable A-lead control -- which means that when the modem is off-hook, it closes a pair of normally-open relay contacts which connect the black and yellow wires in its telephone line cord. The old AT&T modems that don't have built-in auto-dialers were the last ones widely used on dialup circuits that use DSR as described above. -- Dave Levenson Westmark, Inc. The Man in the Mooney Warren, NJ USA {rutgers | att}!westmark!dave